Urinary incontinence, vesicourethral reflux, fecal incontinence, and intrinsic sphincter deficiency (USD), for example, are disorders that have responded to treatments with augmentative materials. Such disorders occur when the resistance to flow of bodily discharges decreases to the point where the resistance can no longer overcome the intra-abdominal pressure. Nearly all procedures developed to restore continence are based on restoring the lost resistance.
Surgical implantation of artificial sphincters has often been employed to treat patients suffering from urinary incontinence. The surgical implantation of the artificial sphincter commonly requires hospitalization, is relatively complex and expensive, and will usually require six to eight weeks of recovery time. Moreover, the procedure may be unsuccessful if the artificial sphincter malfunctions. As a result, additional surgery is required to adjust, repair, or replace the implant.
Urinary incontinence can also be treated using nonsurgical means. A common method to treat patients with urinary incontinence is periurethral injection of a bulking material. One such bulking composition is a Teflon® paste known commercially as “Polytef” or “Urethrin.” This paste is comprised of a fifty-fifty (50-50) by weight mixture of a glycerin liquid with Teflon® (polytetrafluoroethylene (PTFE)) brand particles sold by DuPont. The glycerin is biodegradable, however, and over a period of time the glycerin dissipates into the body and is then metabolized or eliminated leaving only about fifty percent (50%) of the injected mixture (i.e., the Teflon® particles) at the injection site. Consequently, to achieve the desired result, the surgeon typically overcompensate for the anticipated loss of bulking material by injecting a significantly larger amount of material than initially required. At the extreme, this overcompensation can lead to complete closure of the urethra, which could put the patient into temporary urinary retention. Additionally, the eventual dissipation of the glycerin complicates the surgeon's ability to visually gauge the appropriate amount of bulking material to inject. To avoid these over-bulking side effects, the surgeon may ultimately not inject enough bulking mixture, leading to the likelihood of a second or even a third procedure to inject additional material.
Further, the particle size in the Teflon® paste bulking material if sufficiently small may allow the particles to migrate to other locations of the body, such as the lungs, brain, etc. Teflon® particles have been known to induce undesirable tissue reaction and form Teflon® induced granulomas in certain individuals.
In addition, the Teflon® paste is typically highly viscous and can only be injected using a hypodermic needle held by an injection assist device. Use of an injection assist device may be required, because a surgeon would likely not have sufficient strength to force the highly viscous Teflon® paste through a needle of any acceptable size.
Two alternatives to the Teflon® paste are a collagen gel and carbon coated zirconium beads. One such commercially available product includes Contigen®, available from CR Bard. The collagen gel is injected in the same manner as the Teflon® paste and forms a fibrous mass of tissue around the augmentation site. This fibrous mass created by the collagen injection, however, also dissipates over time and is eventually eliminated by the patient's body. As a result, additional injections are periodically required.
Yet another bulking procedure includes the injection of swollen hydrogel particles. The swollen hydrogel particles exhibit relatively low injection forces by incorporating low molecular weight water-soluble organic compounds, along with water, in the particles. See, for example, U.S. Pat. Nos. 5,813,411 and 5,902,832 to Van Bladel et al., and U.S. Pat. No. 5,855,615 to Bley et al., the disclosures of which are hereby incorporated herein by reference in their entireties.
Another alternative to the Teflon paste is a hard particle suspension. One such commercially available product is Durasphere® available from Carbon Medical Technologies. These hard particles, for example carbon coated zirconium beads, are injected in a beta-glucan carrier. The beta-glucan is eliminated by the patient's body over time. As a result, additional injections may be required. Furthermore, hard particle suspensions, depending on the size of the particle, may tend not to be easily dispensed without clogging smaller gauge injection needles.
Furthermore, available methods of injecting bulking agents require the placement of a needle at a treatment region, for example, peri-urethrally or transperenially. Assisted by visual aids, the bulking agent is injected into a plurality of locations, causing the urethral lining to coapt. In cases where additional applications of bulking agent are required (e.g., when bulking agents are dissipated within the body), the newly added bulking agent may need to be injected at a higher pressure than the pressure at which the initial bulking agent was injected. The higher pressure requirements for subsequent injections may result from the effect of closing off the treatment region by the initial bulking agent, thereby creating backpressure when attempting to insert additional hulking agent(s). Typically, the bulking agent is injected at multiple locations to cause the uretheral lining to coapt with a higher opening pressure than the patient had prior to injection of the bulking agent.
Bulking agent delivery methods have attempted to address the issue of subsequent injection requirements. One method that has been employed is hydrodissection of tissue in the vicinity of the treatment region, thereby creating tissue voids designed to decrease the injection pressure required when adding additional bulking agent to the voids. Another method used to reduce injection pressures is the Urovive™ device available from American Medical Systems. Urovive™ utilizes a plurality of silicone balloons that are inserted into the treatment region, specifically, the periphery of the sphincter. The balloons are then filled with a hydrogel to effect tissue coaptation.